1. Technical Field
The disclosure relates to a pre-heat device, more particularly to an injection mold having pre-heating device, the pre-heating device, and method for pre-heating injection mold.
2. Description of Related Art
A conventional procedure for plastic injection molding includes steps as followings: firstly plastic material is introduced to a feeding pipe of an injection molding machine so as to obtain a melted plastic material, secondly, an operation of engaging molds is processed so the melted plastic material can be injected into a die cavity, then, pressure holding of the injection molding machine, cooling, demolding are processed in sequence and finally the finished goods are moved out of the molds.
In the process of injecting molding, the die temperature would influence the shrinkage, deformation, melting engagement lines, and surface brightness of appearance of the finished plastic goods, and also molding circles.
For solving said concerns, a conventional die (oil) heating machine or an electric heating rod is introduced to heat the dies before injection molding. However, keeping the dies in a high-pressure condition through the way, the cooling time and cycle time are prolonged so that the production rate is therefore influenced.
Another application of rapidly cooling/heating dies is passing high pressure steam through a water route installed in the die core, and introduces cooling water through the water route for cooling the dies after the plastic material is injected in the die cavity. Since the water route is distributed inside the die core, disadvantage is that the operation of heating/cooling the die core would be influenced by the heat conduction efficiency of steel material of which the die is made, which leads to more than 20 seconds for transferring heat from the interior of the die core to the surface of the die core.
The other application for pre-heating dies is to utilize petrol/diesel combustion heating stove to generate water steam capable of rapidly passing through a water route installed in the dies. The application consumes relative more energy, and the carbon dioxide emission produced thereby does not meet the environmental protection requirements.
The other one application for pre-heating dies is to utilize flame generated by burning gas. The surfaces of the dies are heated by the flame so the surfaces can rapidly reach high temperature. However, gas burning is not only dangerous and difficult to control the temperature, but also dissatisfied with the requirement of environmental protection.
In view of the mentioned prior arts, how to develop a device and a method for pre-heating die for improving the mentioned disadvantages shall be concerned.